Cruise lines recycle hot water to heat passenger cabins and use special evaporators to distill the water used to cool engines into fresh water for shipboard air conditioning systems – while special window coatings keep cabins and passageways cool with less air conditioning.
Cruise ships generate a number of waste streams that can result in discharges to the marine environment, including sewage, graywater, hazardous wastes, oily bilge water, ballast water, and solid waste. They also emit air pollutants to the air and water.
A June study from sustainable transport campaigner The European Federation for Transport and Environment found that 63 cruise ships owned by parent company Carnival Corporation emitted 43% more sulfur oxides, a group of harmful air pollutants, than all the 291 million cars in Europe in 2022.
Vacuum suction lines zip toilets' contents to marine sanitation farms, which siphon out the water, treat it until it's drinkable, then pump it into the ocean. Helpful aerobic bacteria digest the remaining sludge in storage tanks until it's all offloaded ashore, about once a month.
Onboard Waste Treatment and DisposalThese systems rely on a combination of physical filters, chemical treatments, and even biological processes that can break down and treat human waste. The wastewater treatment systems cruise ships separate solid waste from liquid waste, then they disinfect and treat the water.
Non-native species can colonize, replace and harm local species. Ballast water can also carry diseases like cholera and paralytic shellfish poisoning into our harbors. A single cruise ship produces smokestack and exhaust emissions equivalent to 12,000 automobiles every day.
Cruise ships can harm coral reefs. Pollution from cruise ships can threaten coral reefs. Cruise ships can also damage reefs through collisions and anchors. Recent studies have linked coral diseases to human sewage not unlike what is released from cruise ships.
Common Features of Eco-Friendly Cruise Lines Include:Waste reduction and management: such as composting, recycling, and proper disposal of hazardous materials to minimize waste and pollution. Water conservation: such as using treated greywater for non-potable purposes and reducing water usage through efficient systems.
Cruise Ship PollutionAlthough cruise ships make up only 1 percent of the global fleet, they account for 6 percent of black carbon (BC) emissions. This reveals how disproportionately bad for the environment cruise ships are, releasing the highest amount of black carbon per ship of any vessel.
U.S. law requires cruise ships to treat waste within about 3.5 miles of shore—but beyond that, there are no restrictions on dumping polluted sewage and graywater. Researchers have estimated that over a billion gallons of sludge made from excrement and food scraps are released into the ocean every year by cruise lines.
Cruise ships make their own drinking water. It's unsurprising since they're constantly surrounded by sea water – they use either steam evaporation or reverse osmosis processes to desalinate the water before minerals and chlorine are added. It's the same as a home filtration system, only significantly larger.